The present invention relates to an automotive air cleaner assembly, in particular, an air cleaner assembly having improved adsorber regeneration characteristics.
Recently enacted partial zero emission vehicle (PZEV) standards have encouraged automakers to produce more environmentally friendly vehicles. In order to meet the more stringent emissions requirements, particularly with respect to hydrocarbon emissions, automakers have implemented a number of systems and designs to reduce the emissions both from an engine's exhaust and its air intake. It is known, for example, to incorporate a hydrocarbon adsorber in the air induction system of an engine in order to capture the backflow of hydrocarbons that can occur during engine shutdown. The hydrocarbon adsorber is typically incorporated in the vicinity of a conventional air (particle) filter.
In such air induction systems, hydrocarbons diffusing from the engine can be captured by adsorbent media within the hydrocarbon adsorber thus preventing their release into the environment. The adsorbent media can, in turn, be regenerated during normal engine operation when positive air flow passing through the air induction system entrains the captured hydrocarbons and carries them downstream to the engine where they are combusted.
Automobile engines, including those having a hydrocarbon adsorber, typically include a mass air flow sensor (MAFS). The mass air flow sensor is typically located downstream of the air filter within the air induction system. In order for the mass air flow sensor to provide a measurement having an adequate signal-to-noise ratio, it is preferable that the filter element and its attendant components cause minimal disruption of the air flow reaching the mass air flow sensor.
Prior art hydrocarbon adsorbers, which are typically located directly in the airflow, comprise a mesh or screen that supports the adsorbent media. While such a configuration may reduce the average turbulence in the downstream flow field, it is expensive to manufacture and is susceptible to freezing over during use, which can result in undesired blockage and reduced air flow to the engine.
It is therefore preferable to locate the hydrocarbon adsorber outside of the main air flow. With this geometry, it is possible to minimize both the adsorber's contribution to downstream turbulence and the likelihood that it freezes over during use. One approach to locating the hydrocarbon adsorber outside of the main air flow is to position the hydrocarbon adsorber against an inside wall of the air cleaner assembly. By locating the hydrocarbon adsorber against an inside wall of the air cleaner, however, the air flow that passes through the adsorbent media is reduced, which disadvantageously decreases the efficiency with which trapped adsorbents can be desorbed in order to regenerate the hydrocarbon adsorber.